1. Field of the Invention
The present invention relates to a projection optical system which is employed onto an image display apparatus such as a projector.
2. Description of Related Art
A projection optical system for performing a so-called optical aspect conversion has been suggested, for example, in Japanese Laid-Open No. Hei-5-37948. This projection optical system is adapted to project an image from an image display device such as a liquid crystal display panel in a manner such that the image display device and an enlargedly projected image onto a projection surface have different aspect ratios.
This projection optical system is provided with an anamorphotic lens to its lens optical system to change its magnifying capacity in only the horizontal direction with respect to the vertical direction.
A projection optical system, such as a front projector, having a relatively long projection distance and a narrow angle of view can provide a relatively satisfactory image-forming performance even when being provided with an anamorphotic lens as in the projection optical system suggested by the aforementioned publication. However, a projection optical system, such as a rear projection display apparatus, having a short projection distance and a wide angle of view causes an aberration such as distortion to grow to a non-negligible extent, thereby making impractical the configuration of the projection optical system suggested by the aforementioned publication.